The book has scenes in it the movie did not; the movie contains a very nice denouement the book lacks. The changes made to the story so that it would fit into a movie of reasonable length were entirely logical and nothing important got fucked. I liked the story a lot.
...it's his first novel, and he hit #1 on the NYT bestseller list and got a movie out of the deal. And it's a great read to boot.
I should be so lucky.